Pulp molding die



Sept. 8, 1959 s, CRANE 2,903,063

PULP MOLDING DIE Filed May 6, 1958 INVENTOR ATTORNEY KHRJ. E LouisUnited States Patent ,0

PULP MOLDING DIE Harold S. Crane, Palmer, Mass., assignor to DiamondGardner Corporation, New York, N.Y., a corporation of DelawareApplication May 6, 1958, Serial No. 733,378

8 4 Claims. (Cl. 162-411) This invention relates to pulp molding dies,and more particularly to foraminous dies for molding by suctiondeposition of pulp fibers thereon to produce pulp articles havinglocalized areas of special configuration or design.

In the manufacture of molded pulp articles having intricately shaped orsharply curved and defined areas, considerable difficulty has beenencountered heretofore in the construction of suitable molding dies. Ingeneral, two types of dies have been employed for this purpose, namely,the laminated die and the screen-covered die. The laminated type die isexemplified by Shefiield Patent 1,984,384 and a typical screen-covereddie is disclosed in Chaplin et al. Patent 2,359,201. It has beenrecognized for many years that each of these types of dies possesses itsown advantages and disadvantages, and various proposals have been madeto provide an improved die structure.

Laminated dies are highly adaptable for forming well defined complexshapes, but they are usually undesirably heavy, and they are expensiveto manufacture and to maintain for a sufficiently long useful life.other hand, the screen-covered type dies are relatively inexpensive, butthey are less suitable for the formation of intricately shaped pulparticles, since it is extremely difiicult to shape wire mesh intocomplex and sharply curved patterns without rupturing the wire ordistorting the mesh to such an extent as to alter its drainagecharacteristics and create mechanical weaknesses therein. In order toavoid the difiiculties characteristic of both types of dies, it has beenproposed that a large die surface could be formed by clamping together agreat many small individually screen-covered sections having the desiredcontour, and it has also been suggested that such small individuallyscreen-covered sections could be bolted to the face of a large ordinaryscreen-covered die. However, none of the structures proposed heretoforehave been completely satisfactory for the formation of sharply definedcontrasting localized areas.

An object of the present invention is to provide a new and improved pulpmolding die. ,i Another object of the invention is to provide a new andimproved die structure for molding pulp articles havinglocalizedintricately shaped or sharply curved and defined areas.

Still another object of the invention is to provide a simplified,inexpensive composite die structure having localized areas designed toproduce sharply defined zones of intricate contour, contrasting surfacetexture, or nonuniform thickness in pulp articles molded thereon.

Other objects and the nature and advantages of the instant inventionwill be apparent from the following detailed description, taken inconjunction with the accompanying drawings, wherein:

Fig. 1 is a plan elevation view of a pulp molding die embodying theinvention;

Fig. 2 is an enlarged corresponding view of a portion Of the die asshown in Fig. 1;

On the Patented Sept. 8, 1959 Fig. 3 is a vertical section taken alongline 3-3 of Fig. 2; and

Fig. 4 is a perspective view of a portion of a molded pulp articleproduced on a die embodying the invention.

In accordance with the present invention, foraminous pulp molding diesof conventional screen-covered con struction may be provided withspecially designed localized areas for producing sharply defined zonesof intricate contour, contrasting surface textures, or non-uniformthickness in pulp articles produced thereon, essentially byincorporating a relatively small specially designed laminated moldingdie insert into such conventional screencovered dies. The laminatedinsert is suitably contoured to produce intricate shapes, or othercontrasting effects, as may be desired.

In order to demonstrate the principles of the invention, the molding dieselected for illustration in Figs. 1, 2, and 3 is designed for theproduction of relatively shallow, generally rectangular molded pulptrays having on each of the four sides thereof a relatively smalldecorated area. However, it should be understood that the invention maybe employed advantageously in the manufacture of other molded pulparticles, such as egg trays, pie plates, flower pots, and the like,which may require localized areas of sharply defined contrasting design.

As is best shown in Fig. 3, the illustrated molding die comprises anopen-faced perforated forming plate 10 covering a suction chamber 12,formed in the interior of a generally rectangular die frame 14 havingupstanding end walls 15, said plate having an exterior forming facecontoured to mold pulp trays and a wire mesh screen 16 coveringsubstantially all of the forming face of the plate 10. In the usualmanner, the chamber 12 is adapted for connection to a suitable source ofsuction, which causes pulp fibers to be deposited on the screen 16 whenthe molding die is immersed in a vat containing a thin liquid slurry ofpulp fibers. The outer edges of the screen 16 are secured to the frame14 by means of a retaining ring 18, which is removably fastened to thetops of the walls 15 by a plurality of bolts 20. The inner portions ofthe screen 16 are contoured to fit snugly against the perforated formingplate 10, and due to the inherent stifiness of the wire mesh of whichthis screen is made, it retains this shape. Although the plate 10 in theillustrated embodiment of the invention is shown as a single undividedunit and the screen 16 covers this entire unit, it is contemplated thatthe forming plate 10 may be sub-divided into a plurality of individuallyscreen covered sections which may be clamped together to form a unitaryscreen-covered die.

On each of the four sides of the molding die sho in Fig. 1, localizedareas of contrasting design are formed by laminated inserts 22. In Fig.4 there is shown a portion of a molded pulp tray 24 produced by the dieillustrated in Figs. ,1, 2 and 3, and as depicted in Fig. 4 the inserts22 produce an ornamental projection 26 having three adjacentsemicircular fluted sections 28. The sharply curved and intricatelyformed details of the fluted sections 23 of the projection 26 areclearly defined, and they are in distinct contrast to the surroundingsmooth portions of the surface of the tray 24 which were formed by thewire mesh screen 16.

The laminated inserts 22 are constructed from a plurality of flat lamina30 assembled in compact side-byside relationship, routed or otherwisecut back along one edge thereof to form a contoured molding face 32 oneach insert 22, while the other edges thereof are smooth and even. Thecontoured molding faces 32 are designed to form the adjacentsemicircular fluted sections 28 of the projection 26 on the molded pulptray 24. For this purpose, the molding faces 32 are mounted insubstantial alignment with the forming face of the perforated formingplate 10. Along each contoured face 32 alternate lamina 30 are cut backfarther, as shown at 33 in Fig. 3 to provide drainage channels whichcommunicate with the suction chamber 12 through a channel 34 formed inthe plate 10. Thus, when the entire molding die is immersed in pulpslurry and suction is applied to the chamber 12, excess fluid is drainedtransversely through the cut back portions 33 of the lamina 30 andthence through the channel 34 and the chamber 12, thereby causing alayer of pulp fibers to be deposited onto the molding face 32 of theinsert 22.

Preferably the inserts 22 are mounted in and project through the formingplate 10, and they are seated in and secured to the die frame 14. Theend Walls 15 of the die frame 14 are provided with a plurality ofrecesses 36 into which the laminated inserts 22 are adapted to fitsnugly and be clamped therein by the retaining ring 18. The screen 16preferably extends into and covers at least portions of the sides andbottom of the recesses 36. As a matter of convenience in illustratingthe invention, the inserts 22 are shown mounted in recesses 36 formedonly in the end walls 15 of the die frame 14. However, it is evidentthat inserts of this type may be mounted at any other selected location,such as any portion of the surface of the perforated forming plate 10 ofthe molding die, and in such event it may be desirable to provideenlarged drainage channels within the inserts 22 to insure adequatedrainage into the suction chamber 12.

Molding dies embodying the invention possess all of the advantages ofboth the standard entirely laminated die and the standard screen-coveredtype die used heretofore, while eliminating the troublesomedisadvantages inherent in said prior art dies. Composite diesconstructed in accordance with the invention are particularly useful inthe production of localized areas having attractive surface variations,sharply defined intricate designs, distinctly contrasting surfacetexture, and nonuniform thickness to provide regional ornamentation orstrength.

It will be obvious to those skilled in the art that various changes maybe made without departing from the spirit of the invention, andtherefore the invention is not limited to what is shown in the drawingsand described in the specification, but only as indicated in theappended claims.

What is claimed is:

1. A pulp molding die, comprising a die frame having an interior suctionchamber adapted for connection to a source of suction, a perforatedforming plate covering said chamber, said plate having an exteriorforming face contoured to mold pulp articles, a wire mesh screencovering substantially all of the forming face of said plate, and alaminated molding die insert comprising a compact assembly of laminamounted in a recess provided in the forming plate and having drainagechannels communicating with the suction chamber, said insert having amolding face substantially aligned with the forming face of said plateand contoured to form sharply defined localized areas of contrastingdesign on the surface of pulp articles molded thereon.

2. A pulp molding die, comprising a die frame having an interior suctionchamber adapted for connection to a source of suction, a perforatedforming plate covering said chamber, said plate having an exteriorforming face contoured to mold pulp articles, a wire mesh screencovering substantially all of the forming face of said plate, and alaminated molding die insert comprising a plurality of lamina assembledin compact side-by-side relationship mounted in a recess formed in thedie frame and projecting through the forming plate, said insert having acontoured molding face substantially aligned with the forming face ofsaid plate and having drainage channels communicating with the suctionchamber, said molding face being contoured to form sharply definedlocalized areas of contrasting design on the surface of pulp articlesmolded thereon.

3. A pulp molding die, comprising a die frame having upstanding endwalls and having an interior suction chamber adapted for connection to asource of suction, a perforated forming plate covering said chamber,said plate having an exterior forming face contoured to mold pulparticles, a wire mesh screen covering substantially all of the formingface of said plate, a retaining ring mounted on said end walls forclamping the outer edges of the screen thereto, and a laminated moldingdie insert comprising a plurality of lamina assembled in compactside-by-side relationship mounted in a recess formed in said end wallsand secured therein by the retaining ring, said insert projectingthrough the forming plate and having a contoured molding facesubstantially aligned with the forming face of said plate, alternatelamina being provided with drainage channels communicating with thesuction chamber, said molding face being contoured to form sharplydefined localized areas of contrasting design on the surface of pulparticles molded thereon.

4. A pulp molding die, comprising a die frame having upstanding endwalls and having an interior suction chamber adapted for connection to asource of suction, a perforated forming plate covering said chamber,said plate having an exterior forming face contoured to mold pulparticles, a Wire mesh screen covering substantially all of the formingface of said plate, a retaining ring mounted on the tops of said endwalls for clamping the outer edges of the screen thereto, and alaminated molding die insert comprising a plurality of flat laminaassembled in compact side-by-side relationship mounted in a recessformed in said end walls and secured therein by the retaining ring, saidscreen extending into and covering at least portions of the walls ofsaid recess, said insert projecting through the forming plate and havinga contoured molding face substantially aligned with the forming face ofsaid plate, alternate lamina being cut back below the molding face toform drainage channels communicating through the perforated formingplate with the suction chamber, said molding face being contoured toform sharply defined localized areas contrasting in design with theareas formed by the screen on the surface of pulp articles moldedthereon.

References Cited in the file of this patent UNITED STATES PATENTS1,984,384 Shefiield Dec. 18, 1934 2,273,055 Manson Feb. 17, 19422,600,265 Randall June 10, 1952

